1. Field of the Invention
This invention relates to imaging devices wherein an infrared transparent thermal conductor is heated, and heat is transferred from the conductor through an infrared transparent thermal insulator to an infrared opaque radiator.
2. Prior Art
Devices for producing thermal images are shown in U.S. Pat. Nos. 3,764,839 to Fujimura and U.S. Pat. No. 4,346,901 to Booth.
Fujimura uses a cathode ray tube to heat a face plate and, in turn, heat radiative resistors. Heat sensitive paper is rolled across the radiative resistors to produce a thermal image.
In Booth, a resistive material is disposed between layers of insulation and screen like continuous electrodes. Portions of the insulation are removed at predetermined locations to expose the resistive material and the continous electrodes are fastened to the exposed resistive material. When an electrical potential is applied to the continuous electrodes, the target emits thermal radiation in order to simulate a known thermal image.
Reticulated pyroelectric targets are used to detect infrared radiation. Examples are U.S. Pat. No. 4,317,063 to Pedder, et al, U.S. Pat. No. 4,386,294 to Nelson and U.S. Pat. No. 4,437,035 to Raverdy, et al.
Reticulated pyroelectric targets are used to detect infrared radiation by exposing a signal plate to an image, heating the signal plate with electromagnetic energy from the image which in turn generates an electrical potential difference between opposite faces of the pyroelectric target. The effect of the potential difference is monitored by an electron beam which scans the pyroelectric material on the opposite face from the signal plate. By etching a number of closely spaced grooves into the pyroelectric material, thermal conduction from one spot on the pyroelectric sheet to the surrounding area is reduced thus providing greater image resolution. The technique of using these grooves is known as reticulation.
The prior art does not disclose any device which directly generates an infrared image on an image surface with high resolution and high fidelity (i.e., correlation of the visible image to the true infrared image). Such a device is highly desirable.
Presently, infrared sensor imaging systems are tested by passing an infrared sensor by an object or scene of interest and generating a magnetic tape recording from the sensor. The tape is then utilized to reproduce an electronic image in the test system. But the infrared sensor of the system under test is not tested because no infrared image is actually viewed by its sensor.
The present invention allows the same elecronic signals recorded on the magnetic tape to reproduce a high resolution, high fidelity infrared image. This infrared image can in turn be used to test the infrared sensor of an infrared imaging system.